Background: Online study recruitment is increasingly popular, but we know little about the decision making that goes into joining studies in this manner. In GeneScreen, a genomic screening study that utilized online education and consent, we investigated participants' perceived ease when deciding to join and their understanding of key study features. Methods: Individuals were recruited via mailings that directed them to a website where they could learn more about GeneScreen, consent to participate, and complete a survey. Results: Participants found it easy to decide to join GeneScreen and had a good understanding of study features. Multiple regression analyses revealed that ease of deciding to join was related to confidence in one's genetic self-efficacy, limited concerns about genetic screening, trust in and lack of frustration using the website, and the ability to spend a limited time on the website. Understanding of study features was related to using the Internet more frequently and attaining more information about GeneScreen conditions. Conclusions: The ease of deciding to join a genomic screening study and comprehension of its key features should be treated as different phenomena in research and practice. There is a need for a more nuanced understanding of how individuals respond to web-based consent information.